The invention relates to an intervertebral implant having a core made of a swellable material and having a vertebral-body locating face on its top and/or bottom side, which is connected to the swellable core.
Such an intervertebral implant is described for example in DE 20 2006 005 896 U1. Such an intervertebral implant comprises two end plates made of metal or plastics material, between which is disposed a hydrogel core that is made of a swellable material, which by absorbing water may increase its volume and hence bear a specific structural similarity to a natural intervertebral disk. In order to connect the swellable core to an integral, rigid end plate, in the known intervertebral implant the end plate is provided with thread- or rod-shaped anchoring portions, which extend at a spacing from the end plate and project into the core of swellable material.
Since in the known design a rigid end plate is used, the different expansion behaviour of the end plate made of metal or plastics material, on the one hand, and the swellable core, on the other hand, leads to the production of high shearing forces during the swelling of the swellable material. Such an intervertebral implant moreover has a relatively large cross section because this cross section is determined i.a. by the extent of the end plate.
The object of the invention is to provide an intervertebral implant of the described type in a way that avoids the occurrence of high shearing forces between the vertebral-body locating face, on the one hand, and the swellable core, on the other hand, and moreover facilitates the insertion of the intervertebral implant through a narrow body opening.